[This is strange--and gross--but it works]
On a flight to Vegas I realized that I was going to be sick. I was sitting between a friend and a stranger so I was trying my best not to get sick. I lasted until the plane was pulling in to the gate where my friend handed me one of those convenient little vomit bags--yum. What I realized after I got sick was that I didn't smell vomit. I had been eating soft cream savers all day out of nervousness so when I got sick no one smelled vomit--just a hint of reverse raspberry candy...ahh, it was better than vomit. I tell everyone who travels to stock up on soft cream savers for a "possible sick situation."
FRAME OF MIND is major and determines really whether u vomit or not. I haven't been sick in 14years! Thats because I TELL myself I wont get sick. I just wont let it happen.
Peppermint gum is a big big help,as is massaging your temples, pinching yourself hard as a distraction tool,sitting upright and opening a window for one blast of fresh air.
I find ginger good, either eating ginger biscuits or sipping ginger ale or even sniffing a piece of ginger or the essential oil. With reference to tip above, peppermint gum makes me feel worse although its great if you have been sick to get rid of taste (yuck, sorry).
Fresh air works too, especially on a boat. Avoid the diesel fumes though.
Ginger is a good cure - chewing on a small piece of fresh ginger is best if available.
A few long slow breaths breathing through the nose deep into the belly, holding for 1 or 2 counts before releasing through the mouth often helps me.
It really depends on the cause of your nausea though and if you feel thus way often I'd suggest a visit to a medical practitioner pronto!
Drink a mug of boiling water or as hot as you can bare it. It will either settle your stomach or bring it up. Might not work for travel sickness though, you may need to stick to the Quells
Try not to think about it. If your minds on something else, you wont worry about it as much.
Also, if you feel sick, put you middle finger and index finger on your wrist (as if you were taking your pulse). put pressure on it, and it should ease the sick-feeling.